Unit 8 Lesson 3: Fossil Record and Embryology Flashcards
(22 cards)
Life on Earth is in a constant state of change. Species change over time, and new species evolve from older species. Scientists can find evidence of evolution by comparing the body structures of different organisms over time. This field of study is known as
comparative anatomy
What do comparative anatomists look for
Comparative anatomists look for similarities in the body structures of modern organisms and fossils
Fossil layers
These layers, called strata, are formed at different times with the newest layers on the top. Thus, fossils found in lower strata, which are deeper, are older, and fossils found in the same strata are likely to be remains of plants or animals that lived at the same time.
fossils
Fossils are the remains, imprints, or traces of living things from a previous geological age. Examples include petrified bones, imprints of leaves or footprints, and insects preserved in tree sap.
comparative anatomy
a field of study that compares the structures of embryos to find evolutionary relationships between organisms
Where are fossils often contained
Fossils are often contained in layers of sedimentary rock (rock made from layers of sediment and mud) formed over time.
radioactive decay
the release of energy and/or particles from atoms that are unstable and fall apart over time
To determine the age of the fossils, scientists use a process called radiometric dating. How does it work
This process determines the age of volcanic rock layers above and underneath the sedimentary rock layers by measuring the radioactive decay within the volcanic rock.From this information, scientists can determine the approximate age of fossils in the sedimentary rock layers between the volcanic rocks.
Sometimes, the organisms found within the rock can provide evidence of the environment of the region.
For example, fossil evidence of tropical plants in Antarctica suggest that Antarctica once had a warmer and wetter climate than it does now. Fossils can also show how one type of organism has changed over time. For example, fossils of ancient horses show how the foot of a horse has changed over time.
Scientists can also compare fossils to make a lineage of how a species ? over time.
developed
One limitation of comparative anatomy is that the fossil record is incomplete
Fossils require very specific conditions to form, and organisms with harder body types are more likely to become fossils than soft-bodied organisms. However, scientists can still determine whether there is a common ancestor between organisms, even if they do not have fossil evidence for every species that has ever existed on Earth. As more fossils are discovered, scientists gain a better understanding of how life on Earth evolved.
Scientists also find evidence of evolution in animal embryos (animals that are developing but have not yet been born or hatched).
Many animal species that look and behave differently as adults develop in very similar ways before they are born. The same groups of cells develop in the same order for species that have a recent shared or common ancestor.
An ostrich is a large bird that can reach up to 2.8 meters in height. Ostriches do not fly. Their wings are not large enough to support their large body during flight.
What do the wings of an ostrich tell scientists about the ancestors of an ostrich?
Wings are likely vestigial structures for ostriches. This means that over the course of evolution, these wings lost their function of flight. This suggests that the ancestors of ostriches once had wings that were used for flight.
Scientists can also find evidence of evolution in the anatomy of modern organisms. One example is the presence of vestigial structures.
A vestigial structure is a body part that has lost its function during evolution. The structure once performed an important function for an ancestor of the organism, but it does not have that function today.
Comparative embryology
Comparative embryology is a field of study that compares the structures of embryos to find evolutionary relationships between organisms. By comparing the anatomy of embryos and grown animals, scientists can reveal evolutionary patterns.
How do the fossil record and comparative embryology both contribute to the study of evolution?
The fossil record shows how the body structures of living organisms change over time. Scientists can determine the estimated age of each fossil and put together lineages of organisms. Comparative embryology looks for similarities between animals that are not present in the adult forms. This can be used to find evolutionary relationships between organisms.
what example of embryonic development was given that provides evidence of an evolutionary connection between human beings and fish?
Both human and fish embryos have gills, though the gills in human beings disappear before birth.
Many fossils are found in sedimentary rock—rock made from layers of mud and sediment. Typically, fossils are made up of bones, shells, and other hard body parts. Why
Soft tissue parts, such as skin and hair, often break down over time. In some cases, however, scientists are lucky enough to find the fossilized remains of animal skin and even fossilized embryos, some of which are vertebrate embryos.
Some of the best-preserved fossilized embryos were found in China.
These embryos were from early Cambrian animals that lived 550 million years ago. The Cambrian period is when many groups of complex animals first appeared in the fossil record. These fossils have a jelly-like consistency but, incredibly, are still largely intact.
Researchers investigating these incredibly ancient embryos discovered that the animals may have had a similar life cycle to modern organisms. In fact, the embryos are very similar to those of contemporary corals and starfish.
Scientists have named these embryonic animals “Caveasphaera.” So far, there are no adult fossils of this animal and few similar embryos have been found. Nevertheless, the discovery suggests that the basic building blocks of modern life already existed in Cambrian times.
Do you think the discovery of the embryos in China can be used to determine the evolutionary lineage of modern vertebrates? Use the diagram to support your claim.
Yes, they can. All species evolve from existing species, so vertebrates evolved from more ancient organisms from earlier time periods. Since these Cambrian embryo fossils date back to a time period before vertebrates developed, these fossils can be used to determine the ancient ancestors of modern vertebrates.
​​​Which of the following statements best expresses the importance of embryology to the study of evolution?
Embryology is the most important way to identify relationships among different life forms over time.
Embryology allows scientists to compare living plants to ancient plants.
Embryology is one of several important tools for understanding the process of evolution.
Answer
Embryology is only one of several very useful tools for studying evolution and, as plants have no embryos, it cannot have any impact on the study of plants.
